Treatment of sewage



C. L. PECK.

TREATMENT OF SEWAGE.

APPLICATION FILEDJULY 31.1920.

1,392,213, PatentedSept. 27, 1921.

2 SHEETS-SHEET I.

I N v A QM flflovgfs JUL c. L. PECK. TREATMENT OF SEWAGE. APPLICATIONFILED JU LY 3i, 1920.

Effi? I /Z/// Patented Sept. 27, 1921.

2 SHEETS-SHEET 2.

mm" STATES .cmnnns mm rncx, 61? NEW YORK, N.

" comona'rron Pilgrim orrlca.

Y., ASSIGNOR TO THE D088 comm, L

OF DELAWARE.

rnm'i'umrr or snwaen.

To all whom it may concern.

Bait known that I, CHARLES LEE PECK, a citizen of the United States,residin at New York city in the county of New ork, State of'New York,have invented certain new' and useful Improvements in the Treatment of.S-ewa"ge; and I do hereby declare the following to be a full, clear, andexact descriptionfof the invention, such as will enable others skilledin the art to which it appertains to make and use the same.

This inventionrelates' to the trea ttpent of sewage and similar liquors,such, or example, as domestic ,or municipal sewage, and the like; Theinvention has for its object the provision of certain improvements insewage treatment.

The purification or treatment of, sewage by biological or bacterialaction has, during recent years, been given considerable attention bysanitary engineers. In general, the biological or bacterial action isone of digestion or biological clarification in the course of whichappropriate organisms or bacteria are relied upon to convert putrescibleorganic matter in the sewage into. a non utrescribe or innocuouscondition. Anaero ic or aerobic organisms or bacteria may be made useoffer this purpose. Thus, in accordance with these-called septic tankprocess of sewage treatment,'there is maintained, usually by theexclusion of air and light from the sewage, a condition suitable to thegrowth of anaerobic bacteria, and in the activated sludge process ofsewagetreatment, there is maintained, usually by forced aeration such asthe blowing of air 1n a fine state of subdivision into the sewage, acondition suitable to the growth of aerobic bac-' teria.

Themethod of-sewage treatment contemplated by the present inventiondifi'ers in many respects from eitherthe septic tank or activated sludgeprocesses of purifying sewage, although in certain respects it is in thenature of an activated sludge process. In its complete aspect, themethodof the invention involves four principal operations, namely,

ment in the presence of an accumulation of biological growths or sludge;and (4) acre mentioned operations and the aforementioned combination ofthese four-operations is to be understood as representing my preferredractice.

The improved method of the invention, in its complete as ect, will beexplained in con unct1on wit the accompanying drawin s, in which:

lgure 1 is a diagrammatic flow sheet of an arrangement of apparatus forcarrying out the method of the invention;

Fig. 2 is a sectional elevation of another form of apparatus adapted forcarrying out the aforementioned treatment of the sewage in the presenceof. an accumulation of biological sludge, and

Figf3 is a sectional plan taken on the section line 3--3 of Fig. 2.

Sp clfication of Letters Patent. Patented Sept, 2'1, 1921. Applicationfiled m al, 1920. Serial No. 400,480. v

I have found that with a favorable environment a very effectivebiological clarification or treatment of sewage can be secured in thesewer itself while the sewage is flowing therethrough. Accordingly, the.first operation in my preferred complete method of sewage treatmentconsists in sub j ecting the sewage while it is flowing throifgh thesewer to favorable biological action. -To this end, I have found that itis only necessary to create within the sewage as it flows through thesewer a favorable environment for the development of suitable biologicalgrowths. Usually, there will be present in the sewer bacteria insufiicient numbers or quantity forthe purpbses of the invention, but,where necessary, appropriate bacteria may be introduced into the sewer.Usually,

I find it necessary to stimulate the growth of the bacteria byintroducing into the sewage as it flows throughtthe sewer one or moreagents for stimulating the develop ment of the favorable biologicalgrowths. Where the sewage is for any reason ;oxic' suitable anti-toxicagents may be introduce into the'sewer for overcoming this condi-,

tion. Thus, in accordance with this aspect of the present invention,Iintroduce-mto.

the sewage as it flows, through the sewerone or more agents conducive tothe maintenance within the sewage of a favorable environment for thedevelopment of appropriate biological growths for effecting the desiredclarification or treatment of the sewage. As hereinbefore mentioned,these added agents may consist of appropriate stimulants for the properdevelopment of the biological growths, or of appropriate bacteria, or ofappropriate anti-toxic agents, or of two or' all of such agents.

The introduction into the sewer of one or more of the aforementioned.agents is effected asfar as practicable from the sewer outlet, in orderthat the sewage may secure as complete a treatment as osslble wh leflowing through the sewer. ewer condu1ts or pipes are usually made ofvitr fied tile, brick, or the like, and, in the practice of the presentinvention, the biological growths adhere to and build up on the walls ofthe sewer. The biological growth is a gelatinous velvety mass possessingconsiderable coherence. This biological growth is continually developingand building up on the walls of the sewer and at the same time the flowof the sewage operates to continuously break of? masses of thisbiological growth which thereupon 'commingle with the sewage andeffectively assist in the biological clarification or treatment thereof.At the outlet of the sewer, approfiriate means are established forcollecting and removing the masses of biological growths suspended inthe sewage, or for completing the biological treatment of the sewage, orfor carrying out bothof these steps, as the case may be.

In many cases, the sewage, after having been subjected while flowingthrough thesewer to. the biological treatment contemplatedby the presentinvention, need onl be screened in order to complete the clanfication orurification necessary. In these cases, the llquid which passes throughthescreen may be of a self-purifying character. That is to say, thisscreened iquid may contain favorable organisms in suflicient 5 0.treatment of the sewage wh through the sewer is' inftlienat paratorytreatment a' numbers or quantity to digest withoutnuisance the remainingorganlc matter present in the sewage liquid passing through the screen.Usually, however," the biological is to"- othel p ations for' compl.fication of the sewa Thusfiin age treatment, the-biolo ically treatedsewage discharged fromt e sewer outlet is screened to remove therefromthe lumps or egates of -biological 'growth and is then g? su ected toclarification or partialclanfication in the presence ofan accumulationof cumulation 0 The treatment of the sewage in the pres- I ence of anaccumulation of biological sludge is preferably conducted in relativelydeep or tall tanks. The operation may e carried out as the final step inthe treatment of the sewage or may be carried out as a preparatory stepfor a' subsequent operation. Where the treatment of the sewage in thepresence of an accumulation of biological slud e is the final step inthe purification of t e sewage, the operation is carried out in such amanner as to permit sedimentation of the slud e and decantation of asubstantially clear efliiie t. In other words, the level of the sludgein the treatment tank is maintained sufficiently low, by withdraw- I ingsludge from the lower part of the tank, to insure by decantation asubstantially clear eflluent. .Where the sewage is to be sub,- jected tofurther treatment, no sludge is withdrawn from the tank, but the sewageas a whole is permitted to overflow and is ap-, proprlately conducted tothe next treatment operatlon.

In accordance with my preferred practice, the sewage after treatment inthe resence of an accumulation of biological s udge-is v subjected toaeration in the presence of biological sludge, in substantlally the samemanner as inthe activated sludge process of sewa e treatment In thisoperation, the pun cation and clarification of thesewage 1s completed,and two products are secured, a substantially clear and inocuousefiluent and a biological sludge possessing valuable properties for themanufacture of fertilizers.

If desired, the treatment of the sewage in the presence of anaccumulation of bacterial sludge may follow instead of precede theaeration of the sewage in the presence of activated or biologicalsludge, inwhicgeevent the treatment of the sewage in the p sence of theaccumulation of. biological sludge is carried out, as the final step inthe. treatment process as hereinbefore explained.

- As hereinbefore explained, the additiveagent or agnts'formaintainingwithin the fsewage a favorable environment for the developmentof-appr'opriate biological growths with my preferred complete method ofsew-.

ma be introduced into the sewage while. it

is owing through the sewer .or while undergoing treatme t in thepresence of an acbiological sludge, I or such agent or' agents may beintroduced at-both stages in t e treatment process. Moreover, ifdesired, such agent or agents may be introduced into the sewage whileundergoing aeration in the presence of activated sludge.

While the'biologicaltreatment of the sewactivated sludge air bubbles areforcibly age while fiowing through the sewer and in the presence of anaccumulation of biological sludge is conducted without aeration andwithout the artificial introduction of air into the sewage, whereasduring the aeration ofthe sewage in the presence of passed through thesewage, I have found that in each of these three treatment operationssubstantially similar conditions or en-' vironments are favorable Ito'f'the development of appropriate biological growths for the clarificationof the sewage. For, this reason, the following discussion as to thethrough the sewer or while contained in or flowing through a tank orother appropriate receptacle in the presence of an accumula- ,no toxiceffect upon the sewage.

tion of biological sludge.

I have found that the production and maintenance of a particular rangeof alkalinity or basicity in the sewage is conducive to the growth offavorable biological organisms for clarification of the sewage. I have,moreover, found that the addition of certain metals or metalliccompounds or salts to the sewage exercises a beneficial effect upon thegrowth and development of favora le biological organisms. In particular,have found that metallic iron or certain compounds ofiron such as ironhydroxid or 'carbonate of iron, or similar compounds of iron, when addedto the sewage exercise a very beneficial effect in producing andmaintaining a favorable environment for the development of the desiredbiolog- Instead of the compounds of iron of the character justmentioned, I

ical growths.

have found that similar compounds of other non-toxic metals may be addedto the sewage with beneficial results. Thus, I- may add to the sewagecarbonates "and hydroxids of manganese and the corresponding compoundsoftita ium, aluminum and other metals which beong to the grou known asmetals of the earth oxid group. n general, these compounds may bedefined as insoluble hydroxids of a non-toxic metal or compounds of suchmetals capable of formin an insoluble hydroxid by treatment wit water.metal or compound thereof which exercises The insoluble hydroxid formedbyf'treatment with water results from hydrolysis or hydrolyticdissociation in which the ion of the 1n maintaining a condition which 15a- By non-toxic'I mean to define a water combines with the metallic ionto mineral ertilizer materials, such as'phos phate rock, green sand, andth'ezlik able to the development of the desi logical growths,: and at.the samejtime,

since this material is completely recovered in the final sludge andtherefore adds to the marketable value of the sludge. --I prefer v i.there is no loss of the fertilizer material itself,

to add these inorganic fertilizer materials tothesewage in a finelyground condition,

as, for example, in the form'of a powder which will pass a 300 meshsieve. By selecting inorganic fertilizer material of pro er density. andby regulating the amount ad ed to the sewage, I am able to increase andto control and regulate the anean or average density of the accumulatedsludge, thereby renderin it more readily settleable and moreeasilydewatered and dried. Furthermore, the addition of fertilizermaterials of this general character overcomes in a large measure theusual slimy character of the accumulated sludge, whereby the sludge canbe more readily handled in its subsequent treatment.

Toxic conditions in the sewage may .be satisfactorily overcome by theintroduction into the sewage of appropriate anti-toxic agents. Forexample, where the sewage contains calcium h drate which is injurious tocertain favorab e types of bacteria, such inurious effect may beovercome by the addition to the sewage of a bicarbonate, as, fornstance, potassium bicarbonate; the resulting potassium carbonatebeingitself-a stimulant to the growth of the favorable biologicalorganlsms and being recoverable, to a certam extent, in the bodies oftheorganisms themselves.

Another means ing especially favorable conditions in the sewage for thegrowth of the desirable biological organisms consists in increasi theorganic constituents of the sewage in l to those materials which serveas food for these organisms during theirgrowth. For example, I may addto the sewage certain trade waste liquors such as pack n house which Iemploy for creat-' r spect eflluents, or I may add waste vegetab e. rod-'ucts, such as sawdust, garbage or the li e, or

I also by this means combine a satisfactory disposal of sewage with asatisfactory disposal ofgarbage and at the same timeI recover thefertilizer values of these varlous organic waste products in theaccumulated sludge.

Another advantage of adding certain waste organic materials tothe'sewage lies in the favorable effect produced by certain insolublecellular and fibrous constituents of these waste materials upon theporous character of the accumulated sludge, whereby the sludge isprevented from forming a com-' pact mass upon settling, which cannot bereadily dewatered especially by centrifugal treatment. Also, thepresence of a limited amount of such cellular and fibrous material inthe sludge imparts a more friable'-character to the dried productsludge, thus rendering the product more desLirable fortrans= portationand handling. I n

It will accordingly be understood that in my present process of sewagetreatment, I maintain within the sewage conditions in respect to boththe'inorganic and org a riic constituents of the sewa e which arefavorable to the maximum activity of the desired bioa logical orgamsmsfor effecting clarification" ofthe sewage. On this account it is usuallyunnecessary 1n my resent process of sewage treatment to inocu ate thesewage with any particular organism. The important factor in the presentprocess is the production and maintenance in the sewage of a suitablesup-- ly of inorganioand organic constituents t ereby providing afavorable environment for the developmentof the desired biologicalgrowths. Whenthese conditions are .maintained in the sewage a biologicalfio'ra or growth will usually develop in the sewage' without.inoculationvthich 1s bestsuited to survival in the particular sewagebeing treated and which is also best suited for the production of asatisfactory eflluent and a marketable fertilizer sludge of relatively.

high nitrogen content.

While I do not attribute the advantageous results of. my present processof treating sewage to the predominance of 'any'particular organisms inthe biological growth, I have found that the organisms Bacilluscrenotb/rim and oortz'oelli are as a rule prc-' dominant, and, ingeneral, it appears that an environment whichis favorable to' the"growth and development of these bacilli will purposes of the presentinvention. v

In the event that satisfactory organisms be found a favorableenvironmentfor the for hastening the production of bacterial; growthsof satisfactoactivity. But itis to be understood theta ,that the nature of the base*removed ch inoculation alone- ,will not bring about the desirableresults which the sewage is inoculated may not persist as a predominantconstituent of the biological growth and the activity of the b10-logical growth may become greatly decreased.-

Respecting the degree of alkalinity of the sewage as a whole which Iprefer to employ in the practice of the invention, I have found that asewage which contains about 200 parts per million of base calculated ascalcium carbonate, and using methyl orange indicator in determining theneutral point, is a favorablemedium in which to maintain the activitof'the biological growth at a maximum va us. However, I have foundresent in the sewage exercises an important influence upon the activityof the biological growth. Thus,

such as calcium carbonate, or the like. In

other "words, I prefer that the sewage shall have a hydroxyl ionconcentration varying between about 1x 10 and 1X10 normality, taking1X10 as the hydroxyl ion concentration of pure neutral water This means,

of course, that the sewage may vary from very slightly acid to slightlyalkaline, tak- 111%};1118 water-as the standard of neutrality.

ferring now to Fig. 1 of the accompany ing drawings, there isdiagrammaticai; y

present invention. In this figure I have represented a flow sheetindicating apror cedure "and an appropriate apparatus for practising thepreferred and complete method.

of sewage treatment contemplated by the represented three sewers 5discharging into Q a main sewer conduitfi. At appropriate points 7provision is inade for introducln into the sewers 5 any one or more ofthe a 4 dition agents hereinbefore described. Prefare as far aspracticable I erably, the points 1 v I from the outlet of thesewerjmfllin .6 so that the sewa e maysecure as complete treatment aspossi lewhi-le ,flowing through fore described.- 5 Gelatinous velvety.masses" izo the sewers; 5 and.6.; .'the sewersf5 we Y or aggregatesofbiological growths develop on the walls of the sewer and are from timetotime broken off by thepassage of thefsew age and eomm'ingle therewith.As the sewage flows along, gregates of such biolo ical growths becomemixed with and flow aIong with the sewage. Obviously, the longer thisbiological treatment can be continued the more complete v will be theclarification of thesewage. For

this reason, it is desirable that the biological treatment b e'initiatedas far aspracticable from the sewer outlet. The introduction of additiona ents into the sewer may take place at various ints along the length ofthe sewer, the i ea being in all cases to provide throughout the entirelength of the sewer a favorable environment for the maintenance anddevelopment of the biological growths necessary for effecting thedesired treatment of the sewage while flowing throu h the sewer. I

Following t e biological treatment of the sewage in the sewer conduits,the sewage is subjected to a screening operation in order toremovetherefrom the aggregates ofbiological growths which have collectedthere-- in during the aforementioned treatment. A hollow rotatingcylindrical screen of the construction illustrated in Fig. 1 ofthedrawings is admirably adapted for carryin out this screeningoperation, but it -,wil of course, be understood that other types of ascreenlng apparatus may be employed if deis rotatabl sired. Thescreening apparatus, illustrated in Fig. 1 comprises a screening chamber11 into which the sewage is conducted from the outlet of the sewer 6. Ac lindrical screen 12 mounted in the screening chamber 11. T e screenhas two circular ends 13 and 14, the latter having an axial outlet 20for L ofb cter'l wth' th rdl a la gm m e sewage upwa d well 23 and hasat' its lower end in proxlmpartment 15. The screening medium mayadvantageously be a wire" screen of 25 ga e wire with 20 to 24 meshes tothe inch. The screen may be rotated by means of a pulley 16 from anysuitable ower source, and in practice, I have foun a peripheral speed'of about 200 to 300 feet per minute well adapted for the screening 0eration in hand.

A transverse baflle or li ing member 17 is preferably secured to theface of the W tary screen, and serves to lift the aggregates on theascending side" of the screen, an thereby assists the discharge of suchaggregates into an app 0 riate sludge-collectin compartment 19. elifting member 1 projects about one inch from the external may beremoved in any appropriate manner,

as, for example, by a manually removable cage or perforated basket, orcontinuously by a bucket elevator or similar elevating means.

arge numbers of these agit is of a self purifying character.

tion of this biological sludge ma ing compartment 11, and screenedliquor is continuously discharged through the axial outlet 20 of thescreenin drum into the compartment 15. In certam instances, thisscreened liquor may be directly discharged into rivers or streams, forexample where In most cases, however, it will be desirable, if notnecessary, to subject this screened liquor to further treatment. Thebiological sludge collectin in the compartment 19 may be subjecte to anyappropriate subsequent treatment, and is valuable as a constituent inthe manufacture of fertilizer. Where it is necessary to inocculatethesewage flowing through the sewers 5 with bacteria, a porbe used forthe purpose, being introduce into the sewersat the points 7.

In accordance with my preferred prac- 'tice, the screened liquor fromthe screenin operation is next subjected to biologica treatment in thepresenceof an accumulation of biological growths ior sludge. I prefer toconduct this operation in. a relatively thereof and the screened liquoris introduced beneath the accumulation of biological sludge in the tank.An appropriate a paratus for carrying out this operation 1s illustratedin Fig. 1 of the drawings,

The di sting tank 21,- in which the screened lquor is subjected toblologlcal treatment in the presence of an accumulation of biologicalsludge; is relatively deep jcompared with its diameter, for exam le,

these dimensions may be in the ratio 0 10 feet deep and 6 feet indiameter. VA centrally disposed shaft 22 is rotatably mounted within thetank 21 and carries at 1ts upper end a feeding well 23 into. which thescreened liquid from the compartment 15 the screening apparatus isintroduced througha condult 24:. A depending plpe 25 is carried by andcommunicates with the ity to the bottom of the tank 21 a radiallydisposed member 26 suitably perforated to ermit the discharge of thescreened 11%1101 .mto the bottom of the tank 21. The s aft kept insufiicient motion to prevent the forno i mation of any septic regions inthe tank. A chain 32 and idler plow are preferably asso-.

ciatedwith the rakes 28 for more efi'ectively preventingthe formation ofany septic regions on the bottom or in the corners of the tank 21. Thearrangement and operation of this chain and idler plow will be extentsof the tank.

plained in connection with Fig. 3 of the accompanying drawings.

Where the treatment in the digesting tank 21 is to be the final step inthe treatment of the sewage, the operation is soconducted that thebiological sludge level in this tankis approximately at such a height asis represented by the dotted line a. The tank is provided with anappropriately controlled outlet 29 a short distance below the level (a)of the sludge, and by appropriately controlling the discharge of sludgevthrough the outlet 29 the sludge level within the tankj'maybe maintainedat the desired height and asubstantially clear effluent may use whereany loss in hydrostatic head of the sewage is to be avoided. The tank 21is of the same general character as the tank 21 and has a centrallydisposed rotatable shaft 22'. Near its lower end, this shaft carries avliquid distributer 26 and an arm 27 to which aresecured plows or rakes28'. The sewage to be treated is fed into the distributer 26' frombeneath thebottom bf the tank 21' by means of a pipe 25. .Appropri- 1ate connectionis made between the end of the stationary pipe 25 and thedistributer 26 to permit the rotation of the latter.

A chain 32 is secured to the outer and inner ends of the arm 27, and, inthe rotation of the arm 27"; drags behind the arm and over the bottom ofthe tank 21. A plow 33'is attached to the outer end of the arm 27 bymeans of a chain 34. The face of the plow 33 in contact with the wall ofthe tank 21 is shorter than the other face of the plow, whereby as theplo'w is dragged along by the chain 34 it scrapes the corner of the tankand prevents the formation of an septic spots or regions. In a tank 50in diameter, I have secured excellent results with a'plow 6 inches inheight with its shorter .face 12 inches long and its other face'24inches long, and secured to the arm 27 by a chain 12 to 18 inches inlength. Insuch 'atank, the distributer and rake may advantageously berotated at a speed in the neighborhood of'one-thirtieth R. P. M.

Where the sewage is subjected to aeration which prevents the escape ofair upwardly in the presence of biological slud e after treatment intheaforementioned igesting tank, the valve 29 of this tank is closed, sothatthe overflow from the tank consists of a'mixture of sludge andliquid. Thus, such I0 an amount of material is overflowed from thedigesting tank as corresponds with the raw material fed into this tankand this withdrawn material is conducted to the aeration tank forsubsequent treatment.

The aeration tank, as illustrated in Fig. 1, is substantially circularin section and comprises a cylindrical wall 35 and a substantially fiatbottom 40. The bottom of the tank is provided with appropriate means forthe introduction into the tank of air in a finely disseminated state.To, this end appropriate air compartments 36 are provided in the bottomof the tank and these compartments are covered over or closed by aporous medium 37 which will permit the passage therethrough of air underpressure but which, under the operating conditions, does not permit thepassage'of liquid. I have found filtros tile satisfactory in theconstruction of the porous bottom or medium of the aeration tank, butother materials are available for this purpose.

' A transverse tray orshelf 38, of annular configuration, is arrangedintermediate the top and bottom of the tank. This tray slopes from the.center toward the periphery of the tank and is provided at its outeredge with a plurality of downcast wells 39 com- 'municating with theaeration chamber provided between the bottom 40 of the tank and the tray38. The downcast wells 39 extend into troughs '41, thereby providing aseal through the wells 39.-

in rotating mechanism is operatively suspended within the tank andcomprises a J vertically disposed shaft 42 mounted in suitable bearingscarried by a superstructure (not shown). The rotating mechanism has twosets of radially disposed arms 43 and 44. A series of plows or scrapers45 are secured to each of the arms '43 and 44 and are. arranged to movesettled solid matter from the 'center of the tank toward theperiphery.-. The plows 45 attached to the radial arms 43 are disposed inoperative re lation with the bottom40 of the tank while the plows 45attached to the radial arms 44 are disposed in operative relation to thetop surface of the tray 38. v

The inclined tray 38 divides the tank transversely into a lower aerationchamber and an upper sedimentation and decantationv chamber. Theincoming sewage is fedinto 1215 the aeration chamber from the launder'30 'through aninlet' pi e 46. "The inlet pipe 46: is arranged todischarge the incoming sewage tan'gentiallyacross the bottom of theaeration chamber. A sump 47 is provided bottom 40 of the tank for thecollectionof solid substances of a nature unfitted for circulation withthe sludge and sewage. An appropriately valved outlet pipe 48communicates with this sump '47.

Ac cylindrical ipe or tube 49 surrounds the .shaft 42'of-t e rotatingmechanism and is secured thereto.- The pipe 49 .extends from near thetop of the tank into proximity with the bottom thereof and serves as thedowncast well in which the circulating liquor flows downwardy, as willbe more fully described hereinafter. Surrounding the upper portion ofthe pipe 49 is a cylindrical pipe or, well 50. n the apparatusillustrated in the drawings, the pipe 50 is integralwith' the tray 38and extends upwardly from the central opening in this tray toapproximately the same level as the top of the pipe 49. The concentricpipes 49 and 50 are separated by an appropriate space which serves asthpupcast well for the circulatin liquor. The top of the ipe 50 'isprovide wlth an adjustable over ow lip 51, so thatthe efiective heightof this pipe with respect to the pipe 49 may be adjusted.

The pipe 50 is surrounded by a cylindrical baflie 52 appropriatelyspaced therefrom and secured tothe rotating mechanism. The bafll'e 52extends downwardly from an appropriate distance above the top of thepipe 50 into proximity with the tray 38 and serves the double functionof preventing splashing over of the liquid escaping from the circuit andof conducting this escaping liquid in a-comparatively quiet manner intothe sedimentation and decantation chamber.

The arrangement of the pipes 49, 50 and '52 provides three passages forthe flow of liquid. The pipes 49 and 50 provide a circuit for thecirculation of the liquid in the tion chamber. sewage is subjected tothe elevating action a of the finely disseminated air introducedaeration compartment while the pipes and '52 provide a-passage for theescape'of a certain small fraction of the circulating liquid intothesedimentation and decanta- In the aeration chamber, the

into the liquid through the porous bottom.

By the elevating or air lifting action of the finely disseminated air, acirculation of the sewage is maintained upwardly through the passageprovided between the pipes 49 and 50 and ownwardly" through the pipe49-. Theto of the-pipe 49 is sllghtly lower, for exam e, one inch or so,than the top ofthe over ow Ii 51 of the pipe 52, so that a veryconsiderab e portion of the liquid flowing upwardly through the annularpassagebe tween the two inner pi cs 49 and 50 is returned to theaeration chamber.

A certain percenta e. of the liquid passing upwardly through the annularpassage between the pipes 49 ,and 50 escapes over the O5 lip of thep1pe'50 and flows down through discharge pi the passage provided betweenthe pipes and 52 into a body of similarly treated liq uid undergoingsedimentation and decanta tion in the upper settling chamber of thetank. Sedimentation or settling takes place in the region of the "tankabove the intermediate tray 38 and outside the pipe 52. A certain amountof the liquid in/this settling chamber returns to the aeration chamberthrough the downcast wells 39, and a certain amount of the liquor in thesettling chamber is withdrawn by decantation into a peripheral launder53.

The aeration of the sewage is conducted in the presence of anappropriate amount of biological growth, as in the well known activatedsludge process of sewa e treatment.

The biolog1cal sludge is permitted to settle in the sedimentation anddecanta'tion chamber and an appropriate amount of the settled sludge iswithdrawn through'the sludge eflluent is withdrawn through theperipheral launder 53 and-run to waste, or, if desired, this eflluentmay be-subjected to appropriate treatment for the recovery of suchvaluable substances as it may contain in solution.

As previously stated, in carrying out the present invention, theaeration treatment of the sewage mayrecede the treatment in theaforementione digesting tank. Where the treatment of the sewage 1n thedigestmg tank is the final step in the complete process, it may benecessary to aerate both the efiiuent and the sludge resulting from thistreatment. The treatment of the sewage without artificial aeration inthe presence of an accumulation of biological sludge depletes the sewageof air. The discharge into.

streams or rivers of an efiluent which. is thus depletedof or deficientin air is objectionable since it is injurious to the life of fish andthe I;

like. Moreover, slud e which is lacking in oxygen is difiicult tofer-press. For these 54. A substantially clear reasons, it is generallyadvisable to aerate,

both the efiluent and-the sludge where the treatment in theaforementioned digestingtank is the last step in the sewagepurification.

In the treatment of the sewa ence of an accumulation of bio ogicalsludge without artificial aeration, it is very important that adequateprecautions be taken to prevent any portions or regions of the sewagebecoming septic. A septic condition in in the presa compound of suchmetal capable of forming an insoluble hydroxid by treatment with upontreatment with water forms hydroxid environment.

arrangement hereinbefore described have I 6. The method treating sewagewhich proved very effective in preventing the oc-, currence of septicconditions on the bottom and in the corner of the digestion tank. Thepurpose of. the agitation in the digestion tank is merely to bring thesewage into intimate contact with the biological growths and to preventthe occurrence of any septic condition in this tank. I

I claim: Y

1. The method of treating sewage which comprises subjecting the sewageto biological action in the presence of biological growths favorable tothe clarification of the sewage adjusting the hydroxyl-ion concentration0 the sewage to a value between about 1X10 and l l0', and maintainingwithin the sewage a favorable environment for such biological action byintroducing into the sewage undergoing treatment one or more agentsconducive to the development of said favorable environment.

2. The method of treating sewage which comprises subjecting the sewageto-biological action in the resence of biological growths favorable tothe clarification of the sewage,

and maintaining within the sewage a favorable environment for suchbiological action by introducinginto the sewage a relatively insolublehydroxid of a non-toxic metal or sewage, and maintaining within thesewage a favorable'environment for such biological action by introducinginto the sewage undergoing treatment a compound of iron 'conducive tothe development of said favorable 4. The method of treating sewage whichcomprises subjecting the sewage to biologi-' cal action in the presenceof biological growths favorable to theclarification of the sewage, andmaintaining within the sewage I comprises subjecting the sewage whileflowmaintaining within the sewage a favorable environment for suchbiological action by introducing into the sewage as it flows through thesewer one or more agents conducive to the developmentf'iiisaid favorableenvironment. 7 The method of treating sewage which comprises passing thesewage through a conduit of considerable length and in which there arepresent biological growths favorable to the clarification of the sewage,and stimulating the development of said biological growths by theaddition to the sewage as it flows through said conduit of arela tive'lyinsoluble hydroxid of a non-toxic metal or a compound of such metalcapable of forming an insoluble hydroxid by treatment with water. 7

8, The method of treating sewage which comprises passing the sewagethrough a conduit of considerablelength -and in which there are presentbiological growths favorable to the clarification of the sewage, and

stimulating the developmentof said biological'growths by the addition tothe sewage as it flows through said conduit of a compound of iron whichupon treatmentwith water forms hydrox'id of iron.

' '9. The method oftreating sewage which comprises subjecting the sewageto biological action in the pesence of biological growths favorable to;he clarification of the sewage, maintaining within the sewage afavorable environment for such biological action by introducing 'intothe sewage undergoing treatment one or more agents conducive to thedevelopment of such favorable environment, and subjecting thethustreated sewage to a screening operation for removing therefrom theaggregates of biological growth collecting therein duriiig saidbiological action.

a 10. The method of treating sewage WhlCh comprises passing the sewagethrough a sewer conduit of considerable length and in a favorableenvironment for such biologicaf which there arepresent biologicalgrowths action by introducing into the sewageundergoing treatment acompound of iron which of iron. V

5. The method of treating sewage WhlCh comprises passing the sewagethrough a conduit of considerable length and in which ,there are,present biological growths favorable to the clarification 'of thesewage, andstimulating the development of said biological growths by theaddition to thesew- .age as itflows through said conduit of one orinoreagents conducive tothe'maintenance of a favorable environment for the-developmeiit of said biological growths.

comprises introducing the sewage near favorable to the clarification ofthesewage,

tion for removing therefrom the aggregates of biological lgrowthcollecting therein during said biological action.

11. The method of treatlng sewage which bottom "of 8." mass of sewageundergoing treatment and containing an accumulatlon of the' " with saidaccumulation cumulation of biological growths, whereby the sewage in thecourse of its treatment passes upwardly and in intimate contact ofbiological growths.

13. The method of treating sewage which comprises subjecting the sewageto biological action in the presence of an accumulation of biologicalgrowths, introducing the sewage to be thus treated beneath saidaccumulation of biological growths and pass ing the sewage in the courseof its treatment upwardly through and in intimate contact with saidaccumulation of biological growths, and providing within the mass ofsewage undergoing treatment sufiicient motion to prevent the formationof septic regions.

14. The method of treating sewage which comprises subjecting the sewageto biological action in the presence of an accumulation of biologicalgrowths, introducing the sewage to be thus treated beneath saidaccumulation of biological growths and passing the sewage in the courseof its treatment upwardly through and in intimate contact with saidaccumulation of biological growths, and aerating the product or productsresulting from the aforementioned treatment.

- 15. The method of treating sewage which comprises subjecting thesewage to biological action in the presence of an accumulation ofbiological growths; introducing the sewage to be thus treated beneathsaid accumulation of biological growths and passing the sewage in thecourse of its treatment upwardly through and in intimate contact withsaid accumulation of biological growths, and maintaining withinthesewage undergoing treatment a favorable environment for suchbiological action by introducing into the sewage one or more agentsconducive to' the development of said favorable environment.

16. The method of treating sewage which comprises passing the sewagethrough a conduit of considerable length and in which there are presentbiological growths favorable to the clarification of the sewage,maintaining'within the sewage a favorable environment for suchbiological action by inthe sewer conduit'one or more agents conducive tothe development ofsaid favorable environment, screening the.thus-treated sewage and thereby obtaining a biological sludge and ascreened liquid, and subjectmg said screened liquid to two succeedingtreatment operations in the presence of hiological growths in one ofwhich the sewage 1s artificially aerated and in the other of which thereis no artificial aeration but the sewage is kept in suflicient motion toprevent the' formation of septic regions.

17. The method of treating sewage which comprises passing the sewagethrough a conduit of considerable length andv in which there are presentbiological growths favorable to the clarification of the sewage, andsubjecting the sewage after the foregoing treatment and with or withouta preliminary screening operation to biological act on 1n the presenceof an accumulation of biological growths, introducing the sewage forsaid last mentioned treatment beneath saidlaccumulation of biologicalgrowths and passing the sewage upwardly through and in intlmate contactwith said accumulation of biological growths, and providing within thesewage during the last mentioned treatment suflicient motion to preventthe for- I I mation of septic regions.

18. The method of treatingsewage which comprisespassing the sewagethrough a conduit of considerable length and in which there are presentbiological growths favorable to the clarification of the sewage,maintaining within the sewage a favorable environment for suchbiological action by introducing into the sewage asit flows through saidconduit one or more agents conduciveto the development of said favorableenvironment, and subsequently subjecting the sewage to artificialaeration in the presence of biological growths.

19. The method of treating sewage which comprises passing the sewagethrough a conduit of considerable length and in which there are presentbiological growths favorable to the clarification of the sewage,maintaining within the sewage a favorable environment for suchbiological action by introducing into the sewage as it flows" cbmprisessubjecting the sewage to biological action inthe presence of an accumution of biological growths, introducing the sewage beneath saidaccumulation of biological growths and passing the sewage upwardlythrough and in intimate contact with said accumulation of biologicalgrowths, and subsequently subjecting the sewage to artificial aerationin the presence of biological growths favorable to the-clarification ofthe sewage.

21. The method of treating sewage which comprises subjecting the sewageto two treatment operations in one of which the sewage is artificiallyaerated in the presence of biological growths favorable to theclarification of the sewage and in the other of which the sewage issubjected" to biological action in the presence of an accumulation ofbio-- logical growths but without artificial aeration and in the courseof which the sewage is introduced beneath said accumulation ofbiological growths and passes upwardly through and in intimate contactwith said accumulation of biological growths.

-22. The method of treating sewage which comprises passing the sewagethrough a conduit of considerable length and in which there .are presentbiological growths favorable to the clarification of the sewage, andsubsequently subjecting the sewage with or without a preparatoryscreening operation to two succeeding treatment operations in thepresence of biological growths favorable to the clarification of thesewage, in one of which treatment operations the sewage is artificiallyaerated and in the other of which treatment operations the sewage to betreated is introduced beneath an accumulation of biological growths andpasses upwardly through and in intimate contact therewith and in whichthe sewage is kept in sufiicient motion without artificial aerationtoprevent the formation of septic regions. 1

23. Themethcd of treating sewage which comprises subjecting the sewagewhile flowing through a sewer to biological action, maintainingwithinthe sewage a favorable environment for such biological action byintroducing into the sewage as it flows through the sewer one or moreagents conducive to the development of said favorable environment,subjecting the. thus treated sewage to a screening operation forremoving therefrom the aggregates of biological growthcollecting'therein during the aforementioned biological action,subjecting the screened liquid from the aforementioned operation tobiological action in the presence of anaccumulation of biologicalgrowths in th course of which the sewage is introduced beneath saidaccumulation of biological growths and passes upwardly through and inintimate contact therewith and in which the sewage is kept in suflicientmotion without artificial aeration to prevent the formation of septicregions, and subsequently subjecting the sewage to artificial aerationin the presence of biological growths favorabl to the clarification ofthe sewage.

24. The method of treating sewage which comprises subjecting the sewageto biological action in the presence of an accumulation of biologicalgrowths favorable to theclarification of the sewage in the course ofwhich the sewage is introduced beneath said accumulation of biologicalgrowths and passes upwardly through and in intimate contact therewit andin which the sewage is kept in sufficien otion without artificialaeration to prevent the formation of septic regions.

25. The method of treating sewage which comprises subjecting the sewageto biological action in the presence of an accumulation of biologicalgrowths favorable to the clarification of the sewage in the course ofwhich the sewage is introduced beneath said accumulation of biologicalgrowths and passes upwardly through and in intimate contact therewithand in which the sewage is kept in sufficient motion without artificialaeration to prevent the formationrof septic regions, and subsequentlysubjecting the product or products of the aforementioned treat- .mentoperation to aeration.

26. The method of treating sewage which comprises subjecting the sewageto biological action in the presence of an accumulation of biologicalgrowths favorable to the clarification of the sewage in the cours ofwhich the sewage is introduced beneath said accumulation: of biologicalgrowths and passes upwardly through and in intimate contact therewithand in which the sewage is kept in suflicient motion without artificialaeration to prevent the formation of septic regions, and subsequentlysubjecting the sewage to artificial aeration activated sludge.

27. The methodvof treating sewage which comprises passing the sewagethrough a conduit of considerable length and in which there are presentbiological growths favorable to the clarificationof the sewage,subsequently subjecting th sewage to biological action in the presenceof an accumulation of biologica l growths favorable to the clarificationof the sewage in the course of which the sewage is introduced beneathsaid accumulation of biological growths and passes upwardly through andin intimate contact therewith, and stimulating the development of saidbiological growthsin either or both of the aforementioned treatmentsbyintroducing into the sewage undergoing treatment one or more agentsconducive to the maintenance of a favorable environment for thedevelopment of said biological growths.

In testimony whereof I afiix my signature.

CHARLES LEE PECK.

in the presence of

